Herbert was born in the Stockport area, the son of Samuel and Annie, and was the youngest of their five children recorded on the 1901 census. According to Army records published after the War, Herbert had moved away from the area and was living in Middleton. He returned to Stockport to enlist and was assigned to the Army Service Corps as a driver (service number T2/10506). Newspaper reports suggest that he served with his older brother, Sergeant Thomas Garnett and that, at some point, they were both attached to a Field Ambulance unit of the Army Medical Corps.
At some later point, he was again transferred to the Kings Royal Rifle Corps but, at the time of his death, he had been attached to the above Battalion of the London Regiment (known as Queen Victoria's Rifles). After he was killed, his officer wrote to Thomas, who seems to have been Herbert's next of kin by that time, and was now at home 65 Booth Street, Edgeley with his wife Sarah. "Your brother died a hero. We were trying to take a difficult position when he received his fatal bullet and death was instantaneous". Herbert's death is recorded as being on 27 September but the letter seems to support the view that he died the previous day, when the Battalion attacked in what would later be called the Battle of Polygon Wood.
This was a large scale attack, part of the larger Third Battle of Ypres, which had started on 31 July. Zero hour was at 5.50am and Herbert and his comrades advanced alongside the 2/12th Battalion. They found it difficult to maintain the correct direction due to mist and the very boggy ground and came under heavy enemy fire form Dom Trench and machine guns in a nearby pillbox. There were many casualties. They pressed on, capturing Aviatik Farm, Dear House and Vale House. A strong German counter-attack later forced them out of Aviatik Farm and Dear House. The two battalions were now able to form a defensive position and held this throughout the next day before being relieved.